When a conditional expression is static, where can it be used?

[Georg Bauhaus <rm.dash-bauhaus@futureapps.de>]

A totally meaningless example just to illustrate
the question:  What is it that a compiler must report
for the case statement below, if anything?

procedure CE is

   type DOW is (Mo, Tu, We, Th, Fr, Sa, So);

   procedure P is begin null; end P;

   D: constant DOW := We;
begin
   case D is
      when Mo | We | Fr => P;
      when (if D = We or D = Fr then So else Sa) => P;
      when Tu | Th  => P;
   end case;
end CE;



Georg